Overview

Arundo donax is a perennial grass that can reach up to 20 ft. (6.1 m) in height. Although it can be much shorter when damaged or stressed. The stem resembles a corn stalk.

Foliage

Leaves are long, flat and grow up to 1.5 ft. (0.5 m) long. They can be green or have variegated green and white stripes the length of the blade.

Flowers

Flowering occurs in late summer to early fall, when plants are most easily recognized because of the large, dense flower plumes that develop at the tops of the culms. The plums can grow up to 3 ft. (0.9 m) in length.

Fruit

No fruits or seeds typically outside of its native range. The plant spreads through rhizomes and stem nodes that come in contact with the soil.

Ecological Threat

Arundo donax invades wetlands such as ditches, stream banks and lake shores. Arundo donax competes for water, nutrients and radiation, suppresses and excludes native vegetation which degrades wildlife habitat, increases fire risks and interferes with flood control. Arundo donax is native to India and was introduced into the United States in the early 1800s for ornamental purposes.

General Description

Frequently called a bamboo by many landowners, although from an unrelated part of the grass family.

Arundo donax is a tall, erect, perennial cane- or reed-like grass, 2 to 8 meters high. It is
one of the largest of the herbaceous grasses. The fleshy, almost bulbous, creeping root
stocks form compact masses from which arise tough, fibrous roots that penetrate deeply
into the soil. The culms reach a diameter of 1 to 4 cm and commonly branch during the
second year of growth. These culms are hollow, with walls 2 to 7 mm thick and divided by
partitions at the nodes. The nodes vary in length from 12 to 30 cm. The leaves are
conspicuously two-ranked, 5 to 8 cm broad at the base and tapering to a fine point. The
bases of the leaves are cordate and more or less hairy-tufted, persisting long after the
blades have fallen.[1] There can be variability in leaf and cane dimensions within a stand, possibly in response to water availability.

The flowers are borne in large (3 to 6 dm long) plume-like terminal panicles between
March and September. The spikelets are several-flowered, approximately 12 mm long with
florets becoming successively smaller. The rachilla is glabrous and disarticulates above the
glumes and between the florets. The more or less unequal glumes are membranaceous,
narrow and 3-nerved. They are also slender, pointed and as long as the spikelet. Lemmas
are thin, 3-nerved and pilose. These are narrowed upward with the nerves ending in
slender teeth; the middle one becomes an awn.

It has little or no genetic diversity in California [2] and may be effectively one clone across much of the world.

Stewardship summary

Although Arundo donax has been widely cultivated for a long time, little information on its
biology or ecology has been published. Its rapid growth rate and strong vegetative
competitive ability enables it to quickly invade new areas and dominate local vegetation.
Very little has been published regarding effective ways of controlling arundo and it is
difficult at this point to suggest the best strategy for managing the species.

Natural history

Range

Arundo donax is a native to the countries surrounding the Mediterranean Sea. From this
area it has become widely dispersed, mostly through intentional introduction by man, into
all of the subtropical and warm temperate areas of the world.

Habitat

Arundo donax has been widely planted throughout the warmer areas of the U.S. as an
ornamental. It is especially popular in the Southwest where it is used along ditches for
erosion control.[1] In California, giant reed has escaped cultivation and has
become established in moist places, such as ditches, streams, and seeps in arid and
cismontane regions.[3] As early as 1820 it was so plentiful along the
Los Angeles River that it was gathered for roofing materials.[3]A.
donax tolerates a wide variety of ecological conditions. It is reported to flourish in all
types of soils, from heavy clays to loose sands and gravelly soils.

Plants grow best in well-drained soils where abundant moisture is available.[1]
It can spread from the water's edge up the banks and far beyond the zone previously
occupied by riparian woody vegetation.[4]Arundo donax was observed
to grow well where water tables were close to, or at, the soil surface.[5] Individual plants can tolerate excessive salinity.[1]

Giant reed can be seriously retarded by lack of moisture during its first year, but drought
causes no great damage to patches two- to three-years old.[1] Individuals will
survive extended periods of severe drought accompanied by low-pressure humidity or
periods of excessive moisture.[1] Arundo's ability to tolerate or even grow
well under conditions of extreme drought is due to the development of coarse, drought-resistant
rhizomes and deeply penetrating roots that can reach moisture at depth. A. donax
can survive very low temperatures when dormant but is subject to serious damage by
frosts after the start of spring growth.[1]

Giant reed has played an important role in the culture of the western world through its
influence on the development of music, which can be traced back 5000 years. The basis
for the origin of the most primitive pipe organ, the Pan pipe or syrinx, was made from A.
donax. Reeds for woodwind musical instruments are still made from the culms and no
satisfactory substitutes have been developed.[1]

Even before its musical qualities were appreciated, Egyptians used giant reed as early as
5000 B.C. to line underground grain storage. Mummies of the Fourth Century A.D. were
wrapped in arundo leaves. Other uses for giant reed include: basket-work, garden fences
and trellises, chicken pens, crude shelters, fishing rods, arrows, erosion control, livestock
fodder, pulp and ornamental plants. Medicinally, the rhizome has been used as a sudorific,
a diuretic, as an antilactant and in the treatment of dropsy.[1]

Reproduction

Very little information is available in the literature regarding the biology of A. donax.

Perdue (1958)[1] reports that arundo does not produce viable seeds in most areas where it is
apparently well-adapted, although plants have been grown in scattered locations from seed
collected in Asia. The importance of sexual reproduction to the species, as well as seed viability, dormancy, germination and seedling establishment, have yet to be studied and published.

Much of the cultivation of arundo throughout the world is initiated by planting rhizomes
which root and sprout readily. Wild stands in the U.S. have been reported to yield 8.3 tons
of oven-dry cane per acre [1], and the species is under consideration as a biofuel crop.

Giant reed grows rapidly. Growth rates up to 0.7 meters/week over a period of several
months under favorable conditions is not unusual. Young culms develop the full diameter
of mature canes; further growth involves thickening of the walls. The new growth is soft,
very high in moisture and has little wind resistance.[1]

Condition

Threats

Arundo can rapidly invade streambanks and roadside habitats from a few planted
individuals. When established, it has a strong ability to outcompete and completely
suppress native vegetation. Because it propagates vegetatively, it can form rather pure
stands, often at the expense of other plants.[4] In some areas it may so
totally invade irrigation ditches as to reduce their water-carrying capacity.[3] It also uses large volumes of water itself[6], possibly reducing downstream flow in drier riparian areas. It produces thickets that restrict access to riparian areas, and canes can be flammable in the dry season, and produce floating mats that can impede flow or damage bridges during floods.

A survey of 48 public agencies listed arundo as one of the top 53 weed species of concern.[7] Arundo was nominated for Element Stewardship Abstract research by
preserve managers from Santa Rosa Plateau and Creighton Ranch.

Restoration Potential

With proper management, areas infested with arundo may be restored to more desirable
vegetation. Since arundo may be spread primarily by dispersal of rhizome fragments along
watercourses, removal of the entire rootstock may be adequate to eradicate the plant.
Research is needed to determine the importance of sexual reproduction in this species.

Management/Monitoring

Management Requirements

Weed control involves three fundamental objectives: prevention, eradication and control.

From a practical viewpoint, methods of weed management are commonly categorized
under the following categories: physical, thermal, managerial, biological, and chemical.[8] Physical methods include both manual and mechanical methods. Thermal
methods include both broadcast burning or spot treatment with a flame thrower.
Managerial methods include the encouragement of competitive displacement by native
plants and prescribed grazing. Biological control is usually interpreted as the introduction
of insects or pathogens which are highly selective for a particular weed species. Chemical
control includes both broadcast and spot application.

The most desirable approach is that of an integrated pest management plan. This involves
the optimum use of all control strategies to control weeds. This approach is generally
accepted as the most effective, economical, and environmentally sound long- term pest
control strategy.[8] In cases where more than one control technique is used,
the various techniques should be compatible with one another. Broadcast herbicide
application, for example, may not work well with certain managerial techniques (i.e., plant
competition).

Physical control

The two types of physical control methods discussed below,
manual and mechanical, produce slash debris that can be disposed of by several
techniques. If cut before seeds are produced, debris may be piled and left for enhancement
of wildlife habitat (i.e., cover for small mammals). Debris may be fed through a mechanical
chipper and used as mulch during re-vegetation procedures. Care should be taken to
prevent vegetative reproduction from cuttings. Burning the slash piles is also effective in
disposing of slash.

Manual control

Manual methods use hand labor to remove undesirable vegetation.
These methods are highly selective and permit weeds to be removed without damage to
surrounding native vegetation.

The Bradley Method is one sensible approach to manual control of weeds.[9] This method consists of hand weeding selected small areas of infestation in a
specific sequence, starting with the best stands of native vegetation (those with the least
extent of weed infestation) and working towards those stands with the worst weed
infestation. Initially, weeds that occur singly or in small groups should be eliminated from
the extreme edges of the infestation. The next areas to work on are those with a ratio of at
least two natives to every weed. As the native plant stabilizes in each cleared area, work
deeper into the center of the most dense weed patches. This method has great promise on
nature reserves with low budgets and with sensitive plant populations. More detailed
information is contained in Fuller and Barbe (1985)[9]. Because of arundo's ability to readily recolonize an area, the best results for all control methods have come from systematic control, working from the top of a watershed down, and covering entire watersheds rather than piecemeal control.

Hand Pulling: This method may be used to destroy seedlings or plants up to two meters
tall. Plants or seedlings are best pulled after a rain when the soil is loose. This facilitates
removal of the rooting system, which may resprout if left in the ground. Plants should be
pulled as soon as they are large enough to grasp but before they produce seeds.

Hand Digging: The removal of rootstocks by hand digging is a slow but sure way of
destroying weeds which resprout from their roots. The work must be thorough to be
effective. Every piece of root that breaks off and remains in the soil may produce a new
plant. Such a technique is only suitable for small infestations or around trees and shrubs
where other methods are not practical.

Mechanical control

Mechanical methods use mechanized equipment to remove
above ground vegetation. These methods are often non-selective in that all vegetation on a
treated site is affected. Most mechanical equipment is
not safe to operate on slopes over 30 percent. It is also of limited use where soils are
highly susceptible to compaction or erosion or where excessive soil moisture is present.
Site obstacles such as rocks, stumps or logs also reduce efficiency.

Chopping, Cutting or Mowing:Arundo donax may be trimmed back by tractor-mounted
mowers on even ground or by scythes on rough or stony ground. Unwanted vegetation
can be removed faster and more economically in these ways than by manual means and
with less soil disturbance than with scarification. However, these methods are nonselective
weed eradication techniques. They reduce biological control potential (other
plants outcompeting arundo) and may open up new niches for undesirable vegetation. In
addition, wildlife forage is eliminated. Another disadvantage of chopping, cutting or
mowing is that perennial weeds usually require several cuttings before the underground
parts exhaust their reserve food supply. If only a single cutting can be made, the best time
is when the plants begin to flower. At this stage the reserve food supply in the roots has
been nearly exhausted, and new seeds have not yet been produced. The long-term success of above-ground mechanical removal not in combination with other treatments is questionable.

Prescribed burning (Flame Thrower): A flame thrower or weed burner device can
be used as a spot treatment to heat-girdle the stems at the base of arundo plants. This
technique has advantages of being less costly than basal and stem herbicide treatments and
is suitable for use during wet weather; it cannot be used during periods of wildfire hazard.
Its effectiveness is comparable to manual cutting. The timing of the treatment may affect
resprouting behavior.[10]

Broadcast Burning: Large areas of weed infestation may be burned in order to remove the
standing mature plants. This may be accomplished with or without a pre-spray of
herbicides to kill and desiccate plants, Notably flammable plants usually do not require any
pre-spray treatment. Used alone this method will not prevent resprouting from root
crowns. Burning is best followed by 1) herbicide treatment of stumps, 2) subsequent
burning to exhaust underground food reserves, and/or 3) revegetation
with fast growing native species. Other considerations for the use of prescribed burning
include the time and cost of coordinating a burn, and the soil disturbance resulting from
firebreak construction.

Managerial control

Prescribed grazing: Giant reed is not very palatable to cattle,
but during the drier seasons the animals do not hesitate to graze this species. The younger
shoots are eaten first, followed by the upper parts of the older plants.[11]

In many areas of California the use of Angora and Spanish goats is showing promise as an
effective control for Arundo donax.[12] In the Cleveland National Forest goats
are herded for firebreak management of brush species on over 79,000 acres of land. Goats
are less costly to utilize than mechanical and chemical control methods. They can
negotiate slopes too steep to manage with machines and do not pose the environmental
dangers inherent with herbicides.[13]

A pioneer in the use of goats for weed control in urban settings is Richard Otterstad,
owner of Otterstad's Brush Clearing Service (718 Adams St., Albany, CA 94706, (415)
524-4063). The primary weed control "tools" utilized by Otterstad's company are Angora
goats and light-weight flexible fencing reinforced with electrified wire. Angora's are
preferred over Spanish goats because their smaller size makes them easier to transport
(Otterstad uses a pickup truck). Goats prefer woody vegetation over most grasses or forbs, in varying degrees. They will eat desirable woody vegetation if unprotected

Sheep are more selective than goats in their food choices but function well in grazing
down a variety of plants. Sheep in feeding experiments may survive for extended periods
on a strict diet of Arundo donax[14], thus sheep may be another
practical alternative to mowing.

It is important to properly manage sheep grazing to prevent soil compaction problems
which may occur when sheep are allowed to graze an overly damp area. Sheep are
valuable not only for weed control but also for additional income from the sale of their
wool and their contribution of fertilizer to the soil.

Biological control

The term "biological control" is used here to refer to the use
of insects or pathogens to control weeds. The introduction of exotic natural enemies to
control plants is a complex process and must be thoroughly researched before
implementation to prevent biological disasters. Such tools are not normally suitable for
preserve managers to implement.

A. donax is the subject of an active biological control research program (as of 2006) of the USDA Agricultural Research Service in Texas. Much still needs to be learned about the effectiveness of insects and pathogens at controlling the species. The green bug (Schizaphiz graminum) has been observed to feed on
arundo during the winter.[15] In France Phothedes dulcis
caterpillars may feed on it.[16]Zyginidia guyumi uses A. donax as an
important food source in Pakistan.[17] A moth borer (Diatraea saccharalis)
has been reported to attack it in Barbados.[18]

Please notify the California Field Office of The Nature Conservancy of any field
observations in which a native insect or pathogen is seen to have detrimental effects on
arundo.

Chemical control

Detailed information on herbicides are available in such publications
as Weed Science Society of America (1983)[19] or USDA (1984)[20], and will not be
comprehensively covered here. The Weed Science Society publication gives specific
information on nomenclature, chemical and physical properties of the pure chemical, use
recommendations and precautions, physiological and biochemical behavior, behavior in or
on soils and toxicological properties for several hundred chemicals. In applying herbicides it
is recommended that a dye be used in the chemical mixture to mark the treated plants and
thus minimize waste.

There are several herbicide options available, and translocating herbicides are generally considered the only effective tool for long-term control of large infestations. They are able to kill the rhizomes, and thus minimize the resprouting. As with all methods, returning to the site for up to ten years to spot treat resprouts from surviving rhizomes is the only way to prevent a rapid recolonization of the site. Southern California managers have had success with dye-marked broadcast spraying of a glyphosate solution (which produces a delayed effect but up to 95% kill within 3 months of application; Hong and Leu 1979). Glyphosate is also easy and effective for spot-retreatment and translocates to attack the rhizomes.
Dowpon-C-grass-killer, based on sodium salts of dalapon and TCA, is applied as a full
coverage foliar spray to control deep rooted perennial grasses. Arnold and Warren (1966)[21]
used it at a rate of 15 pounds per 100 gallons (plus 2 quarts of surfactant) in late spring
and summer on A. donax. This rate gave good top growth kill in 2 to 4 weeks. A small
amount of regrowth was evident in 6 months. Fall applications at the same rates resulted
in no regrowth the following spring. Horng and Leu (1979)[22] studied the effects of several
herbicides on arundo in Taiwan. 2,2 DPA at 6-8 kg/ha gave 80% kill within 25
days. Following either glyphosate or 2,2 DPA application with doses of paraquat showed
much faster and more complete control. Paraquat alone at 0.72 kg/ha effectively
controlled arundo. Two applications of paraquat was just as effective as a single
application. Asulam did not adequately control A. donax.

Detailed observations focused on the vegetational change of the affected area over time
will help to determine what method of control would be most efficient.

No quantitative monitoring studies of arundo were discovered in the original preparation of the Element Stewardship Abstract. More may have been created since.

Research

Much more information on seed biology, seedling establishment, growth patterns, and
synecology needs to be gathered about arundo. Of great interest is the importance of
sexual reproduction over vegetative propagation in the establishment of the plant in new
locations. Does arundo produce viable seed in California?

Management research needs include questions such as, what are the most appropriate means of controlling arundo in riparian areas with minimal disturbance to the surrounding native vegetation?